How Raschel Bag Making Machines Work: Yarn to Finished Mesh Sack
A raschel bags making machine is a double needle bar warp knitting line that converts PP, PE or HDPE yarn into open leno mesh sacks in a single pass. The bag is knitted complete on the machine – mesh body, reinforcing ribs, closing rope – and leaves the knitting zone as a continuous roll, which an inline cutting device then separates into individual sacks.
That last step is why this equipment is sold as a production line rather than as one machine: the knitting head, the cutting device and the take-up have to be specified together. A buyer who asks for a bag machine and is quoted a knitting head alone is missing the converting end of the line.
What the knitting elements actually control
The mesh is built by warp knitting, not by weaving. Loop formation sets the three properties a bag is judged on: whether it holds shape under load, whether the aperture stays open, and whether a cut edge unravels in handling.
Per the configuration published on our raschel bag machine page, the element set is an individual needle bar with a tongue bar, plus a stitch comb bar and a knockover comb bar that keep formation even across the width. Four ground guide bars sit above them.
Those four ground guide bars are the number to read on a quotation. They set how much pattern freedom you have, and on a bag line pattern freedom means aperture geometry – the difference between running one bag spec and running a range. The double needle bar principle behind this machine class is covered on our double raschel pages.
Why bags come off as a roll, not as single sacks
On this line the sacks are knitted continuously and wound up; separation happens after knitting. The documented arrangement is an on-line automatic cutting device that takes the finished roll and divides it into single bags, described by PRM-Taiwan in Distinctive Device of Raschel Bag Making Machine.
Continuous knitting is efficient, and it is also what makes fault detection non-negotiable. A single dropped course runs the length of the piece, so an unnoticed fault does not give you seconds – it gives you a full roll that cannot be converted into bags at all.
Our own bag configuration answers that with Laserstop, which halts the machine on a detected fault, and an integrated camera checking fabric quality in real time. On low-margin packaging work that monitoring is protecting yield, not grade.
What the machine can build into the bag
Documented capability across this machine class covers flat and tubular leno bags, knitted-in ribs for load strength, and a closing rope formed at the mouth of the bag so the sack can be tied without a separate converting step.
Materials in use are PP, PE and HDPE, with UV treatment where the bag will sit outdoors – firewood sacks and field-stored produce are the usual cases. The same machine class also produces shade netting, including double-layer shade net.
End products reported by builders in this segment are potato, onion, garlic and apple packaging, firewood bags and produce netting. If your product list looks like that, this is the right family of machine.
Beams: the decision that sets your run length
Bag production is high volume and low margin, so the number that matters day to day is how long the machine runs before it stops. Beam configuration decides it. From our published bag machine specification:
| Configuration | Beam positions | Sectional beam flange |
|---|---|---|
| Standard | Three | 32 in |
| Optional | Four | 21 in |
| Optional | Four | 30 in |
The 32 in standard carries more yarn per beam and suits long uniform runs of a single bag spec. The four-position options trade beam size for feed flexibility, which fits better if you switch mesh types often.
Flange diameter is a plant-level decision, not a machine-level one. Running two flange sizes means two sets of handling equipment and two spares lists, and the doffing crew feels that every shift. Consumable elements for the line are listed on our warp knitting spare parts pages.
Knitted raschel bags against woven sacks
Most buyers reach this machine while comparing two process routes: raschel knitted mesh or woven polypropylene sacking. They are different machines producing different products, not two settings on one line.
| Raschel knitted mesh bag | Woven PP sack | |
|---|---|---|
| Structure | Open knitted mesh; aperture is set at the knitting stage | Closed woven fabric; airflow needs a separate perforation or coating decision |
| Typical products | Potato, onion, garlic, apple, firewood, shade netting | General closed sacking for dry bulk goods |
| Bag shape and pattern range | Flat or tubular, ribs and closing rope knitted in | Outside the scope of this machine class |
| How the market frames it | Marketplace comparison pages put raschel ahead on lightweight and specialty fabric, bag shape variety and smaller custom runs | Framed as the volume route for closed sacking |
The substantive argument for knitted mesh is airflow. Condensation is what spoils produce and degrades stored material, and an open knitted structure manages it passively – no coating, no perforation step, no added cost per bag.
Speed figures, and what they are worth
Published speeds for this machine class need reading with care. Marketplace listings for double needle bar raschel machines in air mesh work state 600 rpm. That is a platform-listed figure for a different fabric on a different setup, not a measured output for bag work, and it does not transfer to your bag spec.
Machine speed is also not output. Output is speed multiplied by working width and by uptime, and on a bag line uptime is dominated by changeover frequency and beam run length rather than by rpm.
If you are specifying a bag line
If you produce mesh packaging in volume for agriculture, retail produce or industrial storage, and your specifications change a few times a season rather than weekly, the standard configuration fits: four ground guide bars for aperture range, three beam positions on 32 in flanges for run length, and fault monitoring to protect yield.
If your specifications change weekly, take a four-position beam option and accept the shorter runs between doffs. If your product is closed woven sacking or coated film packaging, none of this applies – that is a different process. It also does not apply to fine apparel-grade fabric, where the bag element set is the wrong one; that work belongs on the machines described on our raschel warp knitting machine page.
Four figures decide the configuration: bag dimensions, target mesh aperture, yarn type and monthly volume. Send those and a general enquiry becomes a specific quotation in one exchange. Machine enquiries and commissioning run through the group site at grandstarcn.com, with after-sales teams working in Turkey, India, Vietnam, Indonesia and the USA.
Frequently Asked Questions
What is a raschel bags making machine used for?
It knits open leno mesh sacks for produce and outdoor storage – potato, onion, garlic and apple packaging, firewood bags – and the same machine class also produces shade netting, including double-layer shade net. Bags can be flat or tubular, with ribs and a closing rope knitted in.
Are raschel mesh bags knitted or woven?
Knitted. The bag is formed by warp knitting on a double needle bar machine, which is why the aperture, the ribs and the closing rope are all set at the knitting stage. Woven polypropylene sacking is a separate process on separate equipment, not a different setting on this line.
How are the bags separated into single sacks?
The sacks are knitted continuously and wound into a roll, then an on-line automatic cutting device divides the roll into individual bags. That converting step is part of the line, which is why this equipment is normally quoted as a production line rather than as a single knitting machine.
How many warp beam positions should I order?
The standard configuration on our bag machine is three positions for sectional beams with a 32 in flange, which carries more yarn per beam and suits long runs of one specification. Four-position options are available on 21 in or 30 in flanges when you change mesh types often. Standardise on one flange size across the plant.
Which yarns can the machine run?
PP, PE and HDPE are the materials in use across this machine class, with UV treatment specified where the finished bag sits outdoors, such as firewood sacks and field-stored produce. Send your yarn type together with bag dimensions, target mesh aperture and monthly volume, because those four figures decide the beam configuration.
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